11 August 2010—For severely paralyzed, "locked in" individuals, sniffing could become a way to communicate with the outside world. Israeli researchers have developed a device that converts nasal pressure into electrical signals, which could enable paralyzed people to type text, surf the Web, and control wheelchairs.
The researchers, led by Noam Sobel, a professor of neurobiology at the Weizmann Institute of Science, in Rehovot, published initial test results for the device last week in the Proceedings of the National Academy of Sciences. Sniff control is simpler, more robust, and more affordable than other assistive technologies available to the severely disabled, such as tongue control, sip-and-puff (in which users send signals using a strawlike device), and eye tracking, says electrical engineer Anton Plotkin, lead author on the study. He estimates that a market-ready device to control a computer or wheelchair could cost several hundred dollars, compared with the several-thousand-dollar price tag for eye-tracking devices.
Users of the "sniff controller" wear a slender plastic tube in their nostrils. The tube attaches to pressure sensors that are connected via USB to a computer. Software programs convert sniff characteristics—such as magnitude, duration, and direction—into commands that control computer programs or a wheelchair. For instance, a sniff above a certain magnitude translates to a click of a computer mouse or a movement of a joystick. Similarly, in code developed for controlling a wheelchair, two successive inhaled sniffs move the chair forward, and two successive sniffs—one outward, then one inward—move the chair slightly to the left.
This technology caters to patients with locked-in syndrome, who have lost control of all muscles except those around the eye, often because of a stroke or other brain injury. Blinking "yes" or "no" answers and forming words by picking letters that are presented to them by an attendant works as a low-cost form of communication, but the process is very slow and cumbersome. When Jean-Dominique Bauby wrote his memoir, The Diving Bell and the Butterfly, by blinking, it took him two minutes to dictate a typical word.
Besides, some locked-in individuals have only minimal eye control. One such person, who tested the sniff controller for the study, was able to use the device to type at an average speed of one letter every 20 seconds after a few days of practice. Another patient, who has been locked in for 18 years, used the sniff controller to write that the device was "more comfortable and more easy to use" than an eye-movement-tracking device he had tried in the past.
All 10 quadriplegic patients who tested the sniff controller for computer use were able to surf the Internet and type text relatively easily. One quadriplegic man tested the device hooked up to a wheelchair, and with just 15 minutes of practice, he could navigate the chair as well as a nondisabled person. The nondisabled volunteers who tested the device were able to use it as easily as a mouse or a joystick to play a computer game.
But the sniff controller isn’t for everyone. Sniffing strength depends on the position of the soft palate, the tissue in the back of the mouth that controls airflow through the nasal passage. About a quarter of the nondisabled volunteers screened for the study didn’t have enough control over their soft palates to use the device. Still, a sniff-based interface might be a good choice for assistive technology, because sniffing is one of the last brain-control pathways that patients lose in conditions such as amyotrophic lateral sclerosis (ALS, or Lou Gehrig’s disease) and is well preserved in serious brain and spinal cord injuries. "Even if individuals don’t have eye control, they could still have control over the soft palate," Plotkin says.
The researchers admit that brain-computer interfaces (BCIs) might be the most appealing prospect for the severely disabled. So far, such interfaces are available only to a handful of people who are testing them at research centers. They are expensive and difficult to learn to use, says Charles Robinson, director of the Center for Rehabilitation Engineering & Science Technology at Clarkson University, in Potsdam, N.Y. "BCIs would work for [patients] with a long-term prognosis of greater than one year," he says. "They would be impractical for those with less than one year of anticipated life left."
Available assistive technologies, such as tongue control and eye tracking, are preferable for certain conditions, Plotkin says, but they also have drawbacks. Eye tracking costs tens of thousands of dollars and involves video imaging, which might lose accuracy as a wheelchair moves. Sip-puff, which at first glance is similar to sniff control, isn’t appropriate for people who can’t move their heads or are on artificial respirators. Tongue control, meanwhile, can paralyze the tongue muscles after a while.
Robinson says that new ways of communication and control for the disabled are still needed because there is no one-size-fits-all technology. "Rehab is all about niches, and what’s needed is appropriate technology," he says. "Simple is always better. I like the simplicity of sniff control."
About the Author
Prachi Patel is a contributing editor at IEEE Spectrum and a freelance journalist based in Pittsburgh, Penn. In the July 2010 issue she wrote about the engineering employment situation.